Method and system for design of spectral filter to classify tissue and material from multi-energy images

Abstract

A method, system and apparatus for filtering multi-energy images using spectral filtering technique is described. In one embodiment, the method includes obtaining a first image of an anatomical object corresponding to a first radiation energy. In addition, the method includes obtaining at least one additional image, herein called a second image of the anatomical object corresponding to at least one second radiation energy. The at least one second radiation energy is distinct from the first radiation energy. The method also includes determining joint attenuation characteristics of each tissue at the first radiation energy and at the second radiation energy or their derivatives. The method also includes selectively filtering attenuation value in a multi-energy space due to at least one tissue to generate a filtered image from a reference image. The reference image is one of the first image or the second image or their derivatives.

What is claimed is: 
     
       1. A method comprising:
 obtaining a first image of an anatomical object corresponding to a first radiation energy, wherein the anatomical object comprises one or more tissues; 
 obtaining at least one second image of the anatomical object corresponding to at least one second radiation energy, wherein the at least one second radiation energy is distinct from the first radiation energy; 
 determining joint attenuation characteristics of each tissue at the first radiation energy and the at least one second radiation energy; 
 designing a spectral filter for at least one desired tissue from the one or more tissues based at least in part on the joint attenuation characteristics and a mixing proportion of a plurality of constituents of the at least one desired tissue; and 
 selectively filtering using the spectral filter, attenuation values due to the at least one desired tissue from a reference image to generate an enhanced image, wherein the reference image is one of the first image or the at least one second image. 
 
     
     
       2. The method of  claim 1 , further comprising generating a mutual information map between the first image and the at least one second image based on attenuation values of voxels in the first image and attenuation values of corresponding voxels in the at least one second image. 
     
     
       3. The method of  claim 2 , further comprising filtering one or more artifacts from the first image and the at least one second image based, at least in part, on the mutual information map. 
     
     
       4. The method of  claim 1 , wherein the one or more tissues comprise at least one of a bone tissue, a vascular tissue, blood, and a soft tissue, fat, fibrosis and necrotic tissue. 
     
     
       5. The method of  claim 1 , wherein determining joint attenuation characteristics of each tissue comprises computing joint probability density of attenuation response of the each tissue at the first radiation energy and the at least one second radiation energy. 
     
     
       6. The method of  claim 1 , wherein determining joint attenuation characteristics of each tissue comprises computing the joint attenuation characteristics of the each tissue based, at least in part, on a model of the each tissue incorporating at least one of density of the each tissue and composition of the each tissue. 
     
     
       7. The method of  claim 1 , further comprising modeling a joint attenuation response of at least one known tissue at the first and the second radiation energy. 
     
     
       8. The method of  claim 7 , wherein the joint attenuation response is modeled based upon at least one of density of the each tissue, composition of the each tissue, and attenuation characteristics of tissue components. 
     
     
       9. The method of  claim 7 , further comprising classifying the one or more tissues in the first or the at least one second image based, at least in part, upon a plurality of joint attenuation response models for one or more known tissues. 
     
     
       10. The method of  claim 1 , further comprising modeling one or more extreme conditions based, at least in part, upon the joint attenuation characteristics. 
     
     
       11. The method of  claim 1 , further comprising designing the spectral filter for the desired tissue based, at least in part, on noise in the first image and the at least one second image. 
     
     
       12. The method of  claim 1 , wherein determining the joint attenuation characteristics comprises applying local spatial variational analysis, wherein the local spatial variational analysis is determined through at least one of regional sampling, anatomical and data priors, and training from pre-classified data. 
     
     
       13. An image processing apparatus comprising:
 a data acquisition unit configured to obtain a first image of an anatomical object corresponding to a first radiation energy, and at least one second image of the anatomical object corresponding to at least one second radiation energy, wherein the anatomical object comprises one or more tissues and wherein the at least one second radiation energy is distinct from the first radiation energy; and 
 a processor configured to:
 determine joint attenuation characteristics at said one or more tissues at the first radiation energy and the at least one second radiation energy; 
 design a spectral filter for at least one desired tissue from the one or more tissues based at least in part on the joint attenuation characteristics and a mixing proportion of a plurality of constituents of the at least one desired tissue; and 
 selectively filter using the spectral filter, attenuation values due to the at least one desired tissue from a reference image to generate an enhanced image, wherein the reference image is one of the first image or the at least one second image. 
 
 
     
     
       14. The apparatus of  claim 13 , wherein the processor is further configured to generate a mutual information map between the first image and the at least one second image based on attenuation values of voxels in the first image and attenuation values of corresponding voxels in the at least one second image. 
     
     
       15. The apparatus of  claim 13 , further comprising:
 a radiation source configured to generate radiations at various energy levels; 
 a radiation detector array capable of receiving radiations at various energy levels through the anatomical object; and 
 a controller operatively coupled to the radiation source and the radiation detector to control the radiation source and the radiation detector. 
 
     
     
       16. The apparatus of  claim 13 , further comprising an operator console configured to receive input for controlling the apparatus. 
     
     
       17. The apparatus of  claim 13 , further comprising an output device configured to display at least one of input user command, the first image, the at least one second image and the enhanced image.